Impact of 68Ga-PSMA PET/CT on salvage radiotherapy planning in patients with prostate cancer and persisting PSA values or biochemical relapse after prostatectomy

Abstract

BackgroundSalvage radiotherapy (SRT) is clinically established in prostate cancer (PC) patients with PSA persistence or biochemical relapse (BCR) after prior radical surgery. PET/CT imaging prior to SRT may be performed to localize disease recurrence. The recently introduced 68Ga-PSMA outperforms other PET tracers for detection of recurrence and is therefore expected also to impact radiation planning.Forty-five patients with PSA persistence (16 pts) or BCR (29 pts) after prior prostatectomy, scheduled to undergo SRT of the prostate bed, underwent 68Ga-PSMA PET/CT. The median PSA level was 0.67 ng/ml. The impact of 68Ga-PSMA PET/CT on the treatment decision was assessed. Patients with oligometastatic (≤5 lesions) PC underwent radiotherapy (RT), with the extent of the RT area and dose escalation being based on PET positivity.ResultsSuspicious lesions were detected in 24/45 (53.3 %) patients. In 62.5 % of patients, lesions were only detected by 68Ga-PSMA PET. Treatment was changed in 19/45 (42.2 %) patients, e.g., extending SRT to metastases (9/19), administering dose escalation in patients with morphological local recurrence (6/19), or replacing SRT by systemic therapy (2/19). 38/45 (84.4 %) followed the treatment recommendation, with data on clinical follow-up being available in 21 patients treated with SRT. All but one showed biochemical response (mean PSA decline 78 ± 19 %) within a mean follow-up of 8.12 ± 5.23 months.Conclusions 68Ga-PSMA PET/CT impacts treatment planning in more than 40 % of patients scheduled to undergo SRT. Future prospective studies are needed to confirm this significant therapeutic impact on patients prior to SRT.

PSMA Ligands for PET Imaging of Prostate Cancer

“…Several studies have investigated the impact of PSMA ligand PET/CT on patient management and therapy. Most studies have focused on the value of PSMA ligand PET/CT in patients with BCR after curative treatment and have reported changes in therapeutic management depending on the specific clinical scenario and the extent of treatment modification (69)(70)(71)(72)(73)(74). Most recently, an overall change in the therapeutic management of 75% of 131 patients after primary treatment was shown (69).…”

“…Similar results were found in a smaller cohort of 45 patients, resulting in a change of treatment in 19 of 45 patients (42.2%), including extension of radiotherapy field or administration of dose escalation subsequent to local recurrence. In 2 of 19 patients, salvage radiotherapy was replaced by systemic treatment due to multiple metastatic lesions (70). In a well-defined patient cohort before salvage radiotherapy, a major management change in 20 of 70 patients (28.6%) with a PSA level of less than 1 ng/mL was demonstrated by van Leeuwen et al (74).…”

Beyond the androgen receptor II: New approaches to understanding and treating metastatic prostate cancer; Report from the 2017 Coffey‐Holden Prostate Cancer Academy Meeting

“…Retrospective comparison studies have demonstrated PSMA PET may outperform F18-choline, can impact salvage radiotherapy treatment planning, and may guide use of stereotactic body radiation therapy (SBRT) for oligometastatic treatment. [54][55][56][57] Critical validation studies are needed. Recently, PSMA PET has been shown to improve initial staging of prostate cancer compared with MRI and provides complimentary information when utilized together.…”

“…The clinical utility and its ability to impact treatment decisions are less established and are the focus of multiple ongoing clinical trials (NCT02981368, NCT02825875). Retrospective comparison studies have demonstrated PSMA PET may outperform F18‐choline, can impact salvage radiotherapy treatment planning, and may guide use of stereotactic body radiation therapy (SBRT) for oligometastatic treatment . Critical validation studies are needed.…”

Is there a benefit to locally consolidative therapy for oligometastatic non-small cell lung cancer?

“…The trend to treat oligometastatic disease with focally directed radiation technologies is coming at a time when imaging technologies are detecting more areas of asymptomatic disease, and systemic or targeted therapies are allowing patients to continue treatment longer than ever before, tempting clinicians to treat limited metastatic disease more aggressively despite the relative lack of highlevel evidence. In prostate cancer, Ga-PSMA PET scans are detecting areas of distant, low volume disease before biochemical failure after primary radiation or surgery and are radically changing patterns of clinical decisionmaking (19). In breast cancer, advances in systemic therapies have significantly improved survival for those with metastatic disease.…”